Conventionally, some car navigation apparatuses perform right/left turn direction determination. The right/left turn direction determination means specifying an approximate direction of an exit road with respect to an approach road, at an intersection. FIG. 9 shows a bird's-eye view of an intersection as an example of right/left turn direction determination and voice output of the result of the determination.
A vehicle 51 having a car navigation apparatus (not shown) enters an intersection 52 from an approach road 53, and then moves out the intersection 52 to an exit road 54, in accordance with route guidance (a hatched portion is a guide route) by the car navigation apparatus.
Immediately before the vehicle 51 enters the intersection 52, the car navigation apparatus performs right/left turn direction determination. First, an angle θ of the exit road 54 to the approach road 53 is specified from map information. Then, one of multiple directional areas, straight forward direction, diagonal rightward direction, right frontward direction, rightward direction, diagonal right backward direction, right returning direction, returning direction, left returning direction, diagonal left backward direction, leftward direction, left frontward direction, and diagonal leftward direction, is specified as a directional area to which the exit road 54 belongs with respect to the approach road 53. Then, the specified directional area is determined as an approximate direction of the exit road 54 with respect to the approach road 53.
Then the car navigation apparatus outputs, e.g., a voice 57 “Pong, diagonal rightward direction,” as the specified approximate direction.
In the right/left turn direction determination, the car navigation apparatus specifies the approximate direction of the exit road 54 to the approach road 53 simply by determining a directional area to which the above angle θ belongs.
However, in this simple right/left turn direction determination, a user's sense of direction is sometimes shifted from the approximate direction specified by the car navigation apparatus.
For example, in a case where a threshold angle dividing the straight forward direction and the diagonal rightward direction is 15°, if the angle θ in FIG. 9 is 14°, the approximate direction becomes the straight forward direction. Further, if the angle θ is 16°, the approximate direction becomes the diagonal rightward direction. However, even if the angle θ is 16° and the voice 57 “Pong, diagonal rightward direction” is outputted, the user of the vehicle 51 may feel that the direction of the exit road 54 is closer to the straight forward direction from the angle of another road connected to the intersection 52 or the like. In this case, it is unclear for the user whether the voice guidance indicates the exit road 54 or a right side exit road 58 different from the guide route. Further, even if the user understands that the voice guidance indicates the exit road 54 by another guide display, the user might feel “the exit road 54 is in the straight forward direction”?
On the other hand, in many cases, at an intersection, an intersection exit direction is visually displayed with a painted road sign, a road traffic sign on the side of the road and the like. In FIG. 9, a painted road sign 55 is provided on a straight forward lane of the approach road 53 and a painted road sign 56 is provided on a right turn lane of the approach road 53. According to the inventor's study, such display approximately corresponds with a vehicle user's sense of direction. Further, in many cases, these information of visual intersection exit direction are recorded on map data of a car navigation apparatus.